The inventive concept relates generally to electronic memory technologies. More particularly, certain embodiments of the inventive concept relate to memory systems that perform address mapping for a nonvolatile memory device using a bad page map.
Memory devices may be roughly divided into two categories according to whether they retain stored data when disconnected from power. These categories include volatile memory devices, which lose stored data when disconnected from power, and nonvolatile memory devices, which retain stored data when disconnected from power.
Examples of volatile memory devices include static random access memory (SRAM) devices, dynamic random access memory (DRAM) devices, and synchronous DRAM (SDRAM) devices. Examples of nonvolatile memory devices include flash memory devices, read only memory (ROM) devices, programmable ROM (PROM) devices, electrically erasable and programmable ROM (EEPROM) devices, and various forms of resistive memory such as phase-change RAM (PRAM), ferroelectric RAM (FRAM), and resistive RAM (RRAM).
Most nonvolatile memory devices tend to wear out at a rate determined by usage. For instance, flash memory devices tend to wear out at a rate determined by the number of erase or program operations that have been performed. Where certain memory cells are used more often than others, they may wear out sooner, resulting in localized regions of defective or unreliable cells, such as “bad blocks”, “bad pages”, “bad sectors”, and so on.
To preserve reliability in the face of local deterioration, memory systems that incorporate flash memory devices and other types of nonvolatile memory devices typically include mechanisms for managing memory cells that have worn out. One technique is to remap addresses of defective regions to non-defective regions. Such remapping, however, may unduly increase the overhead of memory management, and it may also prevent some pages of memory from being used because they belong to a block that has been deemed worn out.